The invention relates to valves used to control fluid flow in wells.
In a wellbore, one or more valves may be used to control flow of fluid between different sections of the wellbore. These different sections may include multiple completion zones in vertical or deviated wells or in multilateral wells. Various types of valves are available, including ball valves, sleeve valves, flapper valves and other types of valves.
Conventional sleeve valves are mechanically actuated with a tool lowered into production tubing at the end of a slickline or coiled tubing, for example. To actuate the sleeve valve between open and closed positions, the slickline or coiled tubing is raised or lowered at the well surface. Referring to FIG. 1A, portions of a sleeve valve 30 and production tubing 32 are illustrated. The sleeve valve 30 includes a longitudinally moveable concentric sleeve having a port 38 that when aligned with a corresponding port 34 in the production tubing 32 allows fluid flow between the bore 33 and the exterior of the production tubing 32. As illustrated, when the sleeve valve 30 is in the closed position, the body of the concentric sleeve and O-ring seals 36 and 37 block fluid flow through the production tubing port 33. The seals 36 and 37 typically are made of an elastomer material.
Intervention required to operate such mechanically actuated sleeve valves makes them relatively expensive and time-consuming to operate. Because of the depths of some reservoirs, a long slickline may be needed to run an actuation tool downhole. Further, in horizontal or highly deviated wells, the process of moving the sleeve may be very expensive because of the need for coiled tubing or other more complicated actuating mechanisms to carry the tool to the sliding sleeve. Such problems are exacerbated in a well that uses subsea technology, with no platform over the well, in which case an intervention vessel may be needed to access the sea floor to run a tool downhole to actuate the sleeve valve. Further, after a sleeve valve has been exposed to a wellbore environment for some time, the sleeve may be stuck or rendered more difficult to operate due to corrosion and debris. If the sleeve is stuck, then a mechanical jarring device may have to be run into the production tubing to jar the sleeve loose.
In addition, the hydraulic seals formed of an elastomer material may add additional drag to movement of the sleeve valve, rendering its operation even more difficult. Further, due to the presence of the elastomer seals, reliability may be an issue if the sleeve valve is left downhole for a long period of time due to exposure to caustic fluids.
More recently, remotely actuatable sleeve valve systems have been developed. Referring to FIG. 1B, a remotely actuatable sleeve valve system positioned downstream from a packer 20 is illustrated. As illustrated, the sleeve valve system is positioned adjacent a reservoir 12 in a section of a wellbore. A production tubing 10 may be extended to the reservoir 12, which may contain oil or gas, to receive fluid from the reservoir 12 for production to the surface. A sliding sleeve valve 14, longitudinally moveable between open or closed positions, may be mounted either outside the production tubing 10 as shown in FIG. 1B or inside the production tubing as in FIG. 1A. In the open position, ports 15 of the sleeve valve 14 are aligned to corresponding ports in the production tubing 10.
To operate the sleeve valve 14, it may be coupled to an actuator 16 controlled by an actuator drive system 18, which typically may be a linear actuator. Rotary actuators may also be used. In addition, the actuator 16 may be controlled hydraulically or electrically. In response to remotely transmitted electrical signals or hydraulic actuation, the actuator drive system 18 causes longitudinal movement of the actuator 16.
Sleeve valves may require relatively large forces to overcome the drag from hydraulic seals in the valve, particularly when the sleeve valve is exposed to high pressure. In addition, a sleeve valve may require a relatively long stroke to move between a fully open position and a fully closed position. As a result of the relatively large forces and long strokes employed to actuate a sleeve valve, an actuator (such as the actuator system 18 in FIG. 1B) employed to actuate the sleeve valve may need to be relatively high powered. To provide such high power, sophisticated electronic circuitry may need to be employed and relatively large diameter electrical cables may need to be run from the surface to the valve actuator mechanism.
Thus, a need arises for an improved valve system for downhole use in wells.